Allograft-inflammatory factor-1 in rat experimental autoimmune encephalomyelitis, neuritis, and uveitis: Expression by activated macrophages and microglial cells

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Abstract
Allograft inflammatory factor‐1 (AIF‐1) is a Ca2+binding peptide expressed predominantly by activated monocytes. In order to investigate the role of AIF‐1 in autoimmune lesions of the rat nervous system, we have used a synthetic gene to express AIF‐1 in E.coli and have produced monoclonal antibodies against AIF‐1. AIF‐1 was localized to monocytes/macrophages with rather selective staining of a minor rat monocyte subpopulation of lymphoid tissue. We then investigated expression of AIF‐1 in experimental autoimmune encephalomyelitis (EAE), neuritis (EAN), and uveitis (EAU). Within the local inflammatory lesions, infiltrating macrophages are prominently stained. In the diseased brain, AIF‐1‐positive microglial cells are not only found in the direct vicinity of the infiltrate, but widespread activation is seen in the parenchyma. This is the first demonstration that AIF‐1 is present in autoimmune lesions. Immunostaining of microglial cells is noteworthy, as these cells are strategically placed regulatory elements of CNS immunosurveillance. Thus, AIF‐1 might be a valuable marker to dissect the local monocyte heterogeneity in autoimmune disease. GLIA 24:244–251, 1998.